1. Field of the Invention
This invention relates to a spill type swirl injector,
2. Description of the Prior Art
In case the conventional swirl injector is applied to a reciprocating gasoline or diesel engine, the following practical problems arise in the swirl injector, in which the fuel is supplied at an inconstant flow rate while being timely varied or in the swirl injector intermittently injecting the fuel, which is equipped with such a valve device as has communication with a swirl chamber and continuously performs the opening and closing operations of the injector at an extremely high speed.
In this valve device, since the fuel is left, while the valve device is shut off, in the swirl chamber without the swirling energy and is swirled and injected when the valve device is opened, the swirling energy cannot be utilized effectively with a substantial delay in response so that a sufficiently stable liquid film is not established after the valve device is opened, thus allowing coarse droplets to be injected and supplied. Moreover, the valve device cannot be free from such problems in construction and with the precision needed in machining and assembling. And coupled with the technical limitation, both of the fuel atomization characteristics and the response of the fuel injection to the injection pressure cannot be sufficiently expected for the fuel injection under the inconstant flow condition or deteriorated in some cases, which invite various difficulties such as directional instability of the injected fuel and the like. As a result, the aforementioned injection device causes inconvenience in engine operations in its practical use, namely the coarse fuel droplets in the fuel supplied and the intake air cannot be sufficiently admixed to wet the inner wall of the intake pipe with the fuel to thereby fail to effect the desired stable and smooth fuel supply to the combustion chambers so that satisfactory completion of the combustion is so difficult as to invite misfire to thereby deteriorate the drivability of the engine and to invite generation of the noxious gases and poor fuel economy.
For the purpose of overcoming the above-mentioned drawbacks, a spill type swirl injection valve, which forms swirling flow in a swirl chamber at any time by spilling a part of fuel supplied into the swirl chamber, has already been proposed. Namely, a spill type swirl injection valve A.sub.o as shown in FIGS. 1 and 2 in the conventional one.
In the conventional injection valve A.sub.o, a spill opening is arranged to be communicated with a swirl chamber 12 through a fuel spill passage 161. The fuel spill passage 161 is a longitudinal annular passage which is defined between the outer wall of a valve guide 81 for a needle valve 80 and the inner wall of a valve guide bore 5 for a nozzle member 4. The valve guide 81 is placed just above the swirl chamber 12. The spill opening 160 is opened into the needle valve 80 above the valve guide 81 provided with polygonal sides 84 at the outer periphery thereof. The fuel being swirled within the swirl chamber 12 is spilled into the spill opening 160 therefrom through the fuel spill passage 161.
This conventional spill type swirl injection valve A.sub.o, however, has the following practical problems. Since a part of the fuel having a swirling flow is delivered from the swirl chamber 12 through the fuel spill passage 161 placed just above the swirl chamber 12, the fuel is spilled from the outer periphery of the swirl chamber where the swirling flow velocity becomes maximum and also the swirling energy of the fuel is decreased by the axial flow to the fuel spill passage 161. As a result, loss of the swirling energy is remarkable and it becomes impossible to establish intensive or strong swirling flow in the swirl chamber 12 essentially required for improvement of atomization of fuel.
In addition to the above-mentioned drawbacks, the following disadvantages in practical use also arise. Namely, resistance to the swirling flow within the swirl chamber 12 is afforded due to the polygonal sides 84 facing the fuel spill passage 161 so that the swirling energy within the swirl chamber 12 is suppressed by such resistance and, simultaneously, the fuel is required to be spilled from the outer periphery of the swirl chamber 12 where the pressure of the swirling flow becomes minimum. Therefore, it is impossible to satisfactorily spill the fuel.
Accordingly, the conventional spill type swirl injector cannot satisfactorily establish the swirling flow within the swirl chamber 12 so that at the initial time point of injection the injection valve produces dripping of the fuel, a nonuniform flow rate and instability in the injection angle of the fuel. Furthermore, such causes non-uniformity in practice diameters of sprayed fuel.
Thus, the conventional spill type swirl injection valve A.sub.o has many problems which must be solved for its practical use.